I’m a beginner with Fastv8 and generally with wind Turbines, so please excuse me if my question is naive.
I’m trying to compare the blade tip acceleration by using ElastoDyn and BeamDyn.
By reading the output list parameters I saw that with BeamDyn the acceleration is expressed in the global inertial frame coordinate system and with ElastoDyn the acceleration is expressed in the local blade coordinate system. So to compare both acceleration I have to put them in the same coordinate system. My question is : do I only have to change the coordinate system by using the curvature angle furnished by aerodyn and the azimuth angle ?
I already tried to computed this but the results are totally different.
Am I wrong ? Did I miss something ?
Thank you very much for your response,
You are correct that ElastoDyn outputs the absolute blade-tip accelerations but expresses them in the local blade coordinate system. In FAST v8.16, BeamDyn output the absolute blade-tip accelerations and expressed them in the global FAST coordinate system. The transformation you explain neglects the influence blade deflections, the blade-pitch angle, etc.
After releasing FAST v8.16, we noticed this was problematic i.e. that the BeamDyn output could not be easily measured physically and one could not compare ElastoDyn and BeamDyn directly. So, we changed BeamDyn so that it outputs the absolute blade-tip accelerations but expressed in the local blade coordinate system. Although I don’t see that the documentation was updated to reflect this change, this change is included with the updates to BeamDyn in the release of OpenFAST v1.0.0 i.e. TipTAXg is now TipTAXl, etc. I suggest simply upgrading from FAST v8.16 to OpenFAST v1.0.0.